1. Technical Field
The present invention relates to a centrifugal pump and a method of manufacturing a centrifugal pump.
2. Background Art
In the prior art, a blood pump for transporting blood includes a turbo-type pump for delivering blood by a centrifugal force, the pump being provided with a hollow housing, an impeller rotatably encased in the housing, and a rotation shaft being in the rotation center of the impeller (for example, see U.S. Pat. No. 5,575,630). In the blood pump disclosed in U.S. Pat. No. 5,575,630, the housing, the impeller, and the rotation shaft are constituted of separate members which are assembled to manufacture the blood pump. In assembling the blood pump, the rotation shaft and a magnet are first assembled onto the pre-existing impeller, and then the assembled components are encased in the housing. At least one of the rotation shaft or a pivot bearing that receives the shaft is made of a relatively hard material such as metal or ceramic in order to provide sufficient durability to the constant wear that occurs during rotation of the impeller.
Desirable properties of the impeller include compatibility with blood, easy moldability, and transparency. Due to these different considerations, the preferred materials for the impeller are different from the preferred materials for the shaft member. Consequently, the two components have been separately fabricated and then assembled together.
Since the blood pump disclosed in U.S. Pat. No. 5,575,630 has a structure in which the rotation shaft is assembled to the impeller by inserting it into a pre-existing bore formed in the impeller, a slight (minute) gap is unavoidably present between the rotation shaft and the impeller because of manufacturing tolerances and the requirement to make the shaft member insertable. During the use of the blood pump, blood enters into the gap between the rotation shaft and the impeller due to a capillary phenomenon or a pressure difference, which can result in blood clotting and hemolysis during pump operation.